I did a simple belt and pulley change on my LMS3900 to increase the max RPM to approx 4,150 (don't have my tachometer yet) from the 2,500 stock. Thought some of you may be interested in trying it as well.
No machine modifications required.
Total cost around $30
Parts are from https://sdp-si.com/eStore/
PN: A 6A25-032NF1508
PN: A 6R25-M077150
See PDFs attached
GG67
** Disclaimer**
I've made this change but do not have a lot of time running the machine with it to gauge long term bearing life but I'm willing to take the risk for improved RPM and change/upgrade bearings latter if needed.